Learning Forum

[Mansoureh]

Hello everybody,nFor compression test, if we have several strain rate for cross head to compress a structure,for example n10^-4 or 10^-3 (1/s)n and 0.01 , 0.2 and 2 (mm/min)nHow can I recognize which one is static structural analysis , Quasi-Static and Dynamic explicit analysis in Ansys? Is there any rule to figure out ? nI read some topic related to compression test and some expert have told that in compression test time is irrelevant and should we just apply displacement. why should we ignore the time? and why we should not use velocity?nfor simulate this compression rate, should we use transient structural or transient dynamic?nwhen I should use dynamic instead of static analysis? Because some times i see some article use dynamic explicit for 2 mm/min rate of strain for compression test.nyour help is very valuable for me.nThank in advance ...nn

[Sai Deogekar]

Hi,nStatic or Quasi-static analysis is one in which the load is applied very slowly and it ignores any inertial effects. A dynamic analysis on the other hand considers inertial effects. E.g. if a uniaxial compression test is done slowly, then the stress is uniform throughout the body. On the other hand, if the load is applied very fast, you may see stress waves forming throughout the body. In the first case, you would use a Static Structural analysis. In the second one you would use a Transient Structural or Explicit Dynamics analysis. It is beyond the scope of Ansys employees to recommend the rule of thumb for specific strain rates. May be other forum members can chime in.nThis question is beyond the scope of an Ansys employee. Hopefully other forum members can contribute.nI am not sure what you mean by Transient Dynamic, but as discussed in answer 1, if you want to ignore inertial effects, use Static Structural analysis. If you want to consider the inertial effects and the total time to be simulated is large, you should choose Transient Structural analysis. Explicit Dynamics analysis is used when the time to be simulated is very small, e.g. a car crash in which two objects deform a lot in a very short amount of time.nDynamic analysis is used when inertial effects are important. In case of a uniaxial compression text, this might manifest as stress waves that travel throughout the body.nnHope this helps,nSain

[Mansoureh]

Hi @sdeogeka,nThank you for your time to explain for me. Definitely it was useful for me.nWhat about using Autodyn? If I the strain rate be in the range of for example 2 mm/s, should I use Autodyn for solving?nthanks againn